Shaft furnaces for steam-generators



July 16, 1957 H. VORKAUF SHAFT FURNACES FOR STEAM-GENERATORS 2 Sheets-Sheet 1 Filed Nov. 3, 1951 Y Inventor: hLF/W/C/f Vale/yaw: WWW; A

y 6, 1957 H. VORKAUF 2,799,254

SHAFT FURNACES FOR STEAM-GENERATORS Filed Nov. 5, 1951 2 Sheets-Sheet 2 United States Application November 3,

Claims priority,

10 Claims. (Cl. 122-237) The invention relates to shaft furnaces for the com- I bustion of solid fuels in steam-generators and especially to furnaces of the type, in which the air of combustion passes horizontally through a combustion shaft, which is Wholly or partly surrounded by cooled walls.

One object of the invention is the provision of means in such furnaces which prevent the coal or other solid fuel from baking or caking and secure an automatic resliding or resinking of the fuel.

Another object of the invention consists in the provision of means to expose the fuel to high temperature immediately before ignition.

A further object of the invention consists in means to gasify scarcely volatile components of the fuel.

Still a further object of the invention is such a construction of the combustion shaft that the cooling conduits of the rear wall of the combustion shaft do not penetrate the combustion space, in order to prevent that the radiation of the combustion zone is shielded from the fresh fuel.

Still a further object of the invention is a new and improved manner of arranging the cooling pipes with respect to the combustion shaft.

A still further object of the invention is the arrangement of a collecting space or chamber to which the cooling pipes lead. p I I r p A still further object of the invention is the provision of a space underneath the fore-grate, which is in connection with the combustion shaft, preferably stoking devices being provided at the fore-grate.

' Another object of the inventionis the provision of a connecting hole between the combustion shaft and the space beneath the grate of sufficient diameter so that the fuel pile in the shaft may be stoked if desired from the grate zone or through it.

Further objects and advantages of the invention will be made clear fromthe following description in connection with the attached drawings, several examples of a furnace according to the invention.

Fig. 1 is a partial diagrammatic section through a furnace according to the invention.

Fig. 2 is a partial diagrammatic section through another furnace in connection with a steam-generator with compulsory circulation.

Fig. 3 shows diagrammatically a detail with a foregrate and a space beneath said fore-grate.

Fig. 4 shows an arrangement of the cooling pipes similar to Fig. 3.

Fig. 5 shows in partial section a diagrammatic view of a steam-generator with free circulation according to the invention.

Fig. 6 shows a detail scale and Fig. 7 a detail of pestles by which the fuel-bed may be broken up from underneath at the end of the foregrate.

Fig. 8 shows a diagrammatic view, partly in section, of a furnace, the fore-grate being formed by cooling pipes covered with grid plates.

of the grate pipes in an enlarged atent in which Figures 1 to 8 show ner that tubes 3 lead into a Fig. 9 and Fig. 10 show details for the stoking device of the fore-grate.

Referring now to-Figure 1 there is shown a steam-gen erator with free circulation having a shaft furnace, the combustion shaft 1 of which is cooled all round by suitable pipe wall-sections. The pipes or first conduit means 2 of the front wall and pipes or second conduit means 3 spaced from the rear wall extend substantially vertically to form the combustion shaft. Both these conduit means are provided with oblique inner fins 2a, 3a to prevent the fuel from dropping between the pipes. The air of combustion passes about horizontally through the combustion shaft. Coming from the air chamber 4 it passes through the pipe wall adjacent the front wall into the shaft of fuel pile, the

being then discharged through the pipe wall 3. The pipes at the front wall 2 are bent at their upper parts to slant toward the frontal wall of the steam generator, and thus form a fore-grate 5 consisting of cooling tubes or pipes. Also the fore-grate 5 is provided with plates or fins 6 to prevent fuel from dropping through the grate. The fuel slides in layer formation, the height of which may be regulated by a slide 7, from the funnel or bunker 8 onto thefore-grate 5 and it will immediately be highly heated by heat radiation from the combustion chamber or fire zone 9 whereby the fuel is freed from gas and then sinks into the combustion shaft 1 in a more or less ignited state.

Thereby also the hardly volatile components gasify, which would be driven out as tarlike products at a lower temperature and'give rise to a baking or caking of the coal- Advantages are not only obtained for baking fuels but also for fuel which tends to enlarge its volume when heated and which would not have enough space to do so in a shaft provided with a continuous inner surface all round. Consequently a heavy pressure would arise in the shaft causing or aiding to a sticking of the fuel. This difficulty will be relieved by the pre-heating of the fuel before its supply into the combustion shaft.

However, it is important that the cooling pipes do not penetrate the rear wall of-the combustion shaft, since the radiation of the combustion space thereby would be shielded from the fresh fuel. It is preferred to .bend those cooling pipes in the level of the upper mouth of the combustion shaft or to lead them into one or several collectors from which a few pipes drain the mixture consisting of steamand water. Those latter mentioned pipes may even lead through the combustion space without disadvantages.

The tube wall 3 of the combustion shaft together with the rear wall 10 of the combustion space forms a mixing chamber 11 in which the gases of the combustion coming from the shaft mix up before they pass into the actual combustion chamber or space 9. From there the gasses of combustion are drawn off in a downwardly leading boiler funnel, passing successively a contact-heating surface 12, an overheater surface 13 and a preheater surface 14.

The feed-water for the boiler passes to the lower distributors 15 and 16 and to the side-wall distributors 17 through downcomers 18 which may be, other than in the drawing, arranged in angular relation to the boiler plan.

gases of combustion From the upper collectors 19, 20 and 21 .the steam-water mixture is conducted through the drum 22. The segments of the contact heating surface pour out directly into the drum 22. The rear wall pipes 3 of the combustion shaft are bent in a slant upwardly and above the shaft-mouth and form the last row of tubes of the contact heating surface 12. These tubes, when conducted through the combustion chamber space fast ignition and the degasing of the fresh fuel on the fore-grate 5. The connection of therear wall tubes 3 with the drum 22 may alternately be made in such a manhorizontal collector approxi- Patented July 16, 1957 9 would greatly impair the mately in the level of the shaft-mouth. From said collector a few tubes then lead to the drum.

The example according to Figure 2 is a steam-generator with compulsory circulation, in which the fuel sinks from the bunker 8 over the fore-grate 5 into the actual combustion shaft 2. The front and. the rear walls of the combustion shaft itself are formed by inwardly inclined banks of. tube surfaces 23 and '24 staggered and displaced in height relatively to one another. Additional air may be. blown in through tube as a supporting tubefor the cooling pipes of the tube surface 26. Such anarrangement of the combustion shaft gives the advantages that the fuelv is not squeezed or jammed. over the whole length of the shaft, but may expand owin to the openings in the walls.

Other advantages consist in that the interior of the shaft is easily accessible and the fuel-bed may conveniently be stoked through larger apertures 27in the front wall. Since the fuel pile is erected: between the front wall and the combustion. space, no'undesired air may enter the combustion space during stoking. By means of the front tubesurfaces 23 theair entrance side may easily be divided into zones to which thecornbustion air may be conducted in controllable quantities.

The example according to Figure 3 shows-a fore-grate under which there is arranged a free space, communicating with the combustion shaft 1 enabling the gases of combustion to fiow from the shaft 1 through the fore gate 5. By means of the hot gases of combustion the time of outgasing of the fuel will considerably'be shortened.

At the fuel inlet the cooling pipes of the fore-grate 5 are covered with a plate 29 giving a gas-tight closure. The free space 28 beneath. the fore-grate 5 is accessible through a stoking. aperture 30. The cooling pipes 2. of the air inlet side of the shaft 1 are bent to the front and serve for cooling the bottom of the space 28'.

A similar form is shown in Figure 4. In this case the. cooling pipes 2 of the shaft 1' are bent over to the auxiliary grate 31' and pass into the tube surface of'the foregrate 5 so that at the fuel inlet the cooling pipesilieclosely together. Thereby it is prevented that, with partial load, the combustion zone comes too close to. the. fuel bunker 8 and the fuel in the bunker is ignited.

In Fig. 5 there is shown a steam-generator with free circulation havinga combustion shaft 1', the fore-grate of which consists of cooling pipes32 forming part of the circulation path of the stream-generator, said pipes 32 having an annular cross-section. which may be mechanically operated from the outside, guided through theinner space of saidtubes, whiclrmay be pushed into the fuel-bed; The breaking-up of the fuel-bed is thereby effected especially in the zone at the mouth of'the combustion shaft 1, in which baking ofthe fuel or cohering most likely is to-occur. Preferably the front wall 34 of the combustion shaft ismade with a bossing or projection underneath the fore-grate toprovide an enlargement at the shaft inlet, which: makes for an advantageous aiding of the stokingeffect of the pestles. The pestles 33 are operated by means of an operating mechanism 35, which also operates the fuel slide 36. To increase the radiation onto the fore-grate the ceiling of the combustion space iscovered with refractory stones 37.

Fig. 6 shows the designof the grate tubes in an enlarged'scale.v The:circulating Water is let in through pipe 38 into the annular: cross-section. The pestle 33, in its inoperative position, therefore, is in all round cooled surroundngs.

Fig. 7 showsa form of, the. construction of pestle 33,- in which the direction of the. push. is from. below in an angle to the plane of thefore-grate and, therefore, the fuel-bed is to be broken. up from underneath at the. end. of thefore-grate.

According to Figure 8' cooling pipes covered with of the fore-grate are bent the fore-grate 5 is formed by grid plates. The cooling pipes off to an U-shape, and pestles 25-. The air. tube 25 may serve There are pestles 33,

lots 40 and 41, respectively,

39 are arranged in this U-shaped bendings. The manipulation of those pestles effects a breaking-up of the fuelbed on the fore-grate 5 from beneath and at the same time the movement of the fuel to the combustion shaft 1.

Figs. 9 and 10 give further examples for the stoking of the fore-grate. In Fig. 9 the fore-grate 5 formed of cooling pipes is connected with resilient inlets and outthrough which the cooling fluid, especially boiler water, flows to the grate pipes. A vibrator or shaking device 42 gives the impulses for a constant conveying of the fuel from the bunker 8 into the combustion shaft 1 and by its vibration prevents the formation of a fixed bridging of the fuel over the shaft 1.

In the example of Fig. 10 there are grate rods 44 interposed between the frontal cooling pipes 43 of the combustion shaft, which may intermittently be operated vertically by means of a mechanically or manually operated lever arrangement 45. When pushed upwardly they break up the fuel layer at the shaft inlet and aid to the sinking of the fuel;

After having thus described several examples of the invention it will be clear to those skilled in the art that many variations may be made within the scope of the invention, which is limited only by the appended claims.

Having thus described the invention, what is claimed as new and desired to be securedby Letters Patent, is:

1. In a shaft furnace for firing substantially solid fuel and-having-two opposite spaced walls; first conduit means spaced from one of said walls and defining between said first conduit means and said one wall an inlet chamber for fresh air supply,.second conduit means spaced from the other of said Walls'and defining therebetween a combustion gas egress chamber, a fire chamber, said first and second conduit means being spaced from each other and defining therebetween a substantially upright fuel combustion shaft, said fire chamber being positioned above and being in communication with said combustionshaft, said "first and second conduit means being constructed for the passage of cooling fluid, means directing combustion gas from said combustion shaft to said combustion gas egress chamber, and fuel funnel means extending. from outside said furnace toward said fuel combustion shaft for directing fuel to the latter, said fuel funnel means extending sidewardly through said one wall and above said inlet chamber for fresh air supply and including a downwardly inclined fore-grate portion which extends fromsaidone wall downwardly toward said combustion shaft,.whereby fuel supplied through said funnel means over said foregrate portion is at least partially exposed to influences from said fire chamber above said fuel combustion shaft and prior to introduction of said fuel into saidcombustion shaft, thereby preventing adhesion of fuel: particles in said' combustion shaft due to baking andcaking.

2. In ashaft furnace according to claim 1,.wherein said fore-grate portion comprises inclined conduit. means communicating with said first conduit means.

3. In a shaft furnace according to claim 1, including. tube means communicating with said second conduit means and extending upwardly therefrom. toward. said other wall, whereby cooling fluid passed through said second conduit means will enter said tube means and be heated through convection by the gases in the fire chamber thereabove;

4. In a furnace according to claim 1, said first andsecend-conduit means each comprising banks of tubes,.said tube banks of said first conduit means being staggeredv with respect to said tube banks of said second conduit means.

5. In a shaft furnace according to claim 1, said first conduit. means being provided with an extension having an upwardly and outwardly inclined portion below and spaced from said foregrate portion, whereby gases from said combustion shaft enter the space between said extension andsaid fore-grate portion and pass through said fore-grate portion, thereby heating fuel on said fore-grate;

portion prior to introduction of said fuel into said combustion shaft.

6. In a shaft furnace for firing substantially solid fuel and having two opposite spaced walls; first pipe means spaced from one of said walls and defining between said first pipe means and said one wall an inlet chamber for fresh air supply, second pipe means spaced from the other of said walls and defining therebetween a combustion gas egress chamber, a fire chamber, said first and second pipe means being spaced from each other and defining therebetween a substantially upright fuel combustion shaft which communicates with said fire chamber, said fire chamber being positioned above said combustion shaft, said first and said second pipe means being constructed for passage of cooling fluid, at least one of said pipe means diverging from said combustion shaft upwardly and away from said fire chamber, and fuel supply means extending from the side of said furnace and above the inlet chamber for fresh air supply toward said fuel combustion shaft for directing fuel to the latter, said fuel supply means including a portion of said upwardly diverging pipe means forming a fore-grate portion and extending from said one wall toward said combustion shaft, whereby fuel delivered through said supply means above said fresh air inlet chamber and over said fore-grate portion is at least partially exposed to influences from said fire chamber prior to the introduction of said fuel into said combustion shaft, thereby preventing adhesion of fuel particles in said combustion shaft due to baking and caking.

7. In a shaft furnace for firing substantially solid fuel and having two opposite spaced walls; first pipe means spaced from one of said walls and defining between said first pipe means and said one wall an inlet chamber for fresh air supply, second pipe means spaced from the other of said walls and defining therebetween a combustion gas egress chamber, a fire chamber positioned laterally and above said air inlet chamber and laterally and above said combustion gas egress chamber, said first and second pipe means being spaced from each other and defining there- EFL . away from said fire chamber,

between a substantially upright fuel combustion shaft and being in communication with said fire chamber, means connected to said second pipe means directing combustion gas from said combustion shaft to said combustion gas egress chamber, and fuel bunker means extending from outside said furnace through said one wall and above said air inlet chamber toward said fuel combustion shaft and including a fore-grate portion inclined in downward direction from said one wall, said fore-grate portion extending from said first pipe means upwardly and inclined whereby fuel delivered through said bunker means over said fore-grate portion is at least partially exposed to influences from said fire chamber prior to introduction of said fuel into said combustion shaft, thereby preventing adhesion of fuel particles in said combustion shaft due to baking and caking.

8. In a shaft furnace according to claim 7, including ram means projecting into the bed of said fuel on said fore-grate portion,

and means operable from without said furnace to facilitate movement of said ram means.

9. In a shaft furnace according to claim 7, said foregrate portion including spaced U-shaped portions forming parts of said upwardly inclined first pipe means.

10. In a shaft furnace according to claim 7, said second pipe means of said fuel shaft also extending upwardly and inclined away from said fire chamber and terminating in a drum for containing a steam water mixture.

References Cited in the file of this patent UNITED STATES PATENTS Satchwell et al. FOREIGN PATENTS Germany Feb. 5, 1934 Germany V Nov. 2, 1934 Dec. 19, 1950 

